Does Telepathy Exist?

Is a woman's memory superior? What's the evidence for climate change? You ask: we answer!
17 May 2016
Presented by Chris Smith


This week on the Naked Scientists, your questions go under the microscope. Do women have a superior memory? What is the evidence for climate change? Can plants get cancer? Why do we sometimes see stars? And has the universe been through multiple big bangs? Join Dr Chris as he puts an astrophysicist, a neuroscientist, a climate researcher and a plant scientist through their paces tackling the questions you've been sending in...

In this episode

Toilet sign

Do women have better memories than men?

We asked neuroscientist Kate Storrs to help restore marital bliss for Mpho...

Kate - I love how much personal bitterness there is in this question. It's certainly something that people believe. A recent study found that 70% of people believe that women have slightly better memories than men if you just survey popular opinion. There is a fair bit of science on it with very mixed results.

Chris - Usually it relates to how often you put the rubbish out - that kind of thing.

Kate - It certainly does depend what it is you're trying to remember. It's one of those situations where you want to turn to meta-analysis (big gatherings of many studies) to try and make sense of the conflicting results. One recent meta-analysis of 123 studies that had looked at verbal memory (memory of sentences and words, memory for spatial location of object, and memory for faces) found that about 60% of these studies had found slightly better performance in women and most of the remainder found no gender difference. So, there does seem to be a bit of evidence that, statistically, women might have slightly better memories but like all gender differences it's a very small effect. So this individual man and his wife are hard to be informed by the very messy science.

Chris - If there is a difference, then it must have some kind of evolutionary reason for being there. So what might be the reason it's there, if it is?

Kate - No, absolutely not. It could have a totally cultural reason. So, for example, there's a study that found that women have better memories for faces while men have better memory for cars and, presumably, the explanation for that is just that men tend to be more interested in cars and have more prior knowledge within which to slot a new car. So, it can be total societal and cultural.

Chris - But, at the same time, can you not argue that there is a genetic element to men or boys being more interested in certain things than girls. I have a son and a daughter, and my son - I thought we'd made a breakthrough the other day because he said he was building something with some lego and it was a tower. And I thought well that's good because it's not a weapon because everything else is a weapon. And I said what's the tower for and he said that it's for my gun. Whereas my daughter just makes houses and draws pictures.

Kate - There most certainly are some real genetically driven cognitive differences between men and women. Even infant Macaque monkeys - the female infants - there's some evidence that the prefer more delicate games and more motor skill kind of games, while the boys enjoy gross motor skills smashing rocks on ground kind of games.

Arabidopsis - a model plant

Can plants get cancer?

We've all heard about Cancer in people and dogs but Howard Griffiths lets us know if plants can get it too...

Howard - Well that's a very interesting question and, intriguingly, we think that some of the regulatory elements - the things that trigger cancers in animal systems - well, those processors were first discovered in plants, actually.

Chris - What do you mean by regulatory systems?

Howard. Well, little genes that get produced - small RNAs that come out and edit gene expression. They actually control whether genes get turned on or off or whether that protein gets made and that's what causes these cells to start growing uncontrollably.

Chris - In humans and animals when you have a cancer you have, as you say, uncontrolled cell growth. This is a genetic problem and one of the characteristics of cancers is that the cells spread around the body, so can you get a similar phenomenon in plants?

Howard - Well, most of the cancerous types of growths that we see in plants are rather more localised. Often sorts of things that you might see are what used to be known as a "robin's pincushion" or even the "witches broom" that you see on Birch and that's often caused by a bacterial infection.

Chris - And what does the bacterial infection do?

Howard - It triggers cells to uncontrollably grow, it changes their hormone balance and because of that you then get this outgrowth.

Chris - So you can get something that's a bit like cancer but it's not the same sort of systemic problem that you get in a person?

Howard - Exactly.

Chris - But a lot of the genetic changes are common to both plants and people?

Howard - Yes, indeed. In fact the bacterial system, that's how we used to transfer genetic material from plant to plant (the bacterium called agrobacterium).

The HARPS measurement reveal the presence of three planets with masses between 10 and 18 Earth masses around HD 69830, a rather normal star slightly less massive than the Sun.

What would the planets do without the sun?

We asked Astronomer Gerry Gilmore what he thought of this one...

Gerry - The planets would keep moving exactly as they are, instantaneously. People imagine that planets naturally move in circles, but they don't. Everything naturally moves in a straight line. A planet moves a little bit in a straight line and it falls a little bit towards the sun, and it moves a little bit more and falls towards.

Chris - And that's gravity tugging it inwards?

Gerry - Yes, that's right. It's falling the whole time but it's also moving in a straight line the whole time. So, if the gravity were simply to stop, the planets would just continue in the straight line they are currently moving in, that's the tangent as we call it, to their present orbit, and so they would just carry on moving away. The underlying presumption here is when all this happens is kind of interesting because people imagine that there is some sort of and absolute underlying time, a newtonian time, and that therefore all the planets will head off instantaneously at the same time. But, actually, time is different on the different planets so it takes time for gravity, and light, and everything else to come from the sun to us.

Chris - Ah right, so gravity isn't there instantly. What you're saying is if the sun did evaporate all of a sudden in an instant, then we wouldn't know for a certain amount of time.

Gerry - Exactly. If the sun suddenly went dark, then the sky would stay bright for as long as it took the light to get to us.

Chris - So you're saying that gravity propagates at the speed of light?

Gerry - Yes and so does time, actually. Everything goes at the speed of light. Both time and gravity and light all travel at the speed of light.

Chris - Why do we think that gravity propagates at the speed of light then?

Gerry - We know it does actually, it was measured early this year.

Chris - With the gravitational wave stuff?

Gerry - With the gravitational wave burst, yes.

Chris - And how did they measure that then?

Gerry - There were two detectors separated by a finite distance and you could measure the time.

Chris - The gravity wave arrives at one and they know how far away it is to the other one?

Gerry - Yes, and a few milliseconds later the other one which was a few thousand kilometers away and that's fundamental to Einstein's general theory of relativity, was a prediction from almost immediately after the theory was developed, and it was completely different than the way it works in newtonian gravity where there is this absolute time sitting there in the background that things just live in, whereas we now know that that's not correct.

Chris - So to summarise for the benefit of Munyuradzee who sent this question in. Were the sun or a star with some planets going round it suddenly to disappear it's gravitational influence would be removed, and the time it took before those planets ceased to feel the gravity from that star would be however long it takes light from that star to reach that planet.

Gerry - Absolutely. So if you're outside watching it you would see the planets popping off in their straight line orbits but, because everything happening in the time it takes the signal to get to you, you'd see it all just vanishing off very nicely. It's only if you were one one of those planets you'd think it was different.

Polar Bear

Is climate change really happening?

Dan Jones seperated fact from fiction...

Dan - Whenever I think about climate change I don't usually start with the temperature trend, like you're suggesting, I'd start with carbon dioxide. We know that carbon dioxide is a greenhouse gas that was measured in the mid 1800s and any spectroscopy lab in the world can see the wavelength of radiation that carbon dioxide likes to absorb and emit. We know that it absorbs every from the earth's surface and then emits energy back down to the earth's surface.

Chris - By energy you mean heat? To make it simple. We're talking about basically infrared energy aren't we. Heat?

Dan - Yes, infrared, that's fine.

Chris - So what you're saying is the more CO2 that there is because it can absorb more of that energy, there's more opportunity for that energy to be soaked up?

Dan - If you put more CO2 in the atmosphere you will get more energy down here at the surface, that's really clear. We've been adding about 30 billion tons of carbon dioxide per year and that accumulates in the ocean, atmosphere, and land and that's from fossil fuel burning. The short story is that that energy has to go somewhere. If you double carbon dioxide that's energetically equivalent to putting a 4 watt light bulb on every square metre of the earth's surface and letting it run 365 days a year, 24/7. 4 watts might not sound like a lot but the earth is gigantic, so if you put one of these light bulbs in every square metre, that ends up being energetically equivalent to about 40 nuclear explosions per second, which is.

Chris - Okay. So the physics argument is that because there's more of something that can soak up the energy around there should, therefore, be more opportunity to interrupt that energy before it goes off into space and the earth's system should become warmer, so that's what the physics says. But what people are saying is when you look at graphs and things like that there appears to be some disparity between what the carbon dioxide's doing, what the temperatures doing, what the current climate measurements and predictions are doing. How do climate scientists like you respond to those sorts of allegations?

Dan - Right. What the gentleman who asked the question was referring to was the surface temperature - just land surface temperature. Well not just land but the surface temperature and that quantity can be affected by how energy is exchanged between the atmosphere, and the ocean, and the cryosphere. So, if that's the only number you're looking at you will see some wiggles, it will rise, it will fall and some of that is just due to exchanges of energy between the different parts of the climate system. An easier to read thermometer, I might suggest, would be something like ocean heat content. It takes more energy to raise the temperature of the ocean by 1 degree than it does the atmosphere because you can put a lot more heat into the ocean - it has a higher heat capacity. So, if you look at the ocean heat content for the past several decades, it has been increasing and it looks steadier than the surface temperature, which does have some of these increases and decreases.

Chris - So, is it fair to say that the general trend is an upward one for both the surface temperature and also the sea temperature? That there are fewer wiggles in the sea than there are at the surface, which you would expect because the ocean it takes a lot more energy in the ocean so it's going to be a lot more stable over time? We would expect to see wiggles in the atmosphere because there are going to be changes and variations year on year anyway, but the general trend is an upward one?

Dan - That right, so I wouldn't get too caught up in looking at one year or even a couple of years. I'd look at several decades, the past century or so.

A pair of In-N-Out cheeseburgers

What is the gallbladder for?

Chris Smith lent us his expertise to answer this question...

Chris - Well the gallbladder is a small bag which is attached to your bile duct or your biliary tree which comes off your liver. So the gallbladder sits underneath the liver. The common reason why people have the gall bladder removed is because the develop gallstones and these produce a symptom called capillary colic.

Classically people complain of a pain at the right upper part of their tummy after or around the time that they're eating a very fatty meal. Now this is because the gallbladder stores bile. The liver makes bile and it secretes the bile into the biliary tree, the bile runs down the bile ducts, drains into the gallbladder, which opens up, relaxes and fills with this bile. Bile consists of bile salts and cholesterol and things called phospholipids, and these are chemicals that are stored in the gallbladder temporarily and then used when you eat a fatty meal to come out into the small intestine through your bile duct, and mix with the fats and break them up or emulsify them into lots of small droplets that your digestive juices can more easily act on.

But because the bile is full of these fatty materials, sometimes they can form stones and these stones build up like gravel in the gallbladder and they can block the neck of the gallbladder, so that when it tries to contract and expel the bile instead a stone can get stuck in the neck and it makes it very painful, and this is the biliary colic.

Surgeons, when a patient presents with these symptoms and they diagnose gallstone disease go in, usually with cameras, which are put in through one or two small holes in the abdomen and then they remove the gallbladder just using these telescopes - it's called laparoscopic surgery. It's very safe, it's very effective at relieving the symptoms and, usually, patients have absolutely no symptoms afterwards that their gallbladder has been removed. The biliary tree has enough capacity to store enough bile so that, as long as you don't overdo it on eating a fatty meal, you shouldn't even notice that you've no longer got you gallbladder, apart from not having the gallstones any more.

So, I hope that gives you some reassurance Ruth, and good luck.

virginia live oak

Why don't trees make the ground subside?

We put this question to plant scientist Howard Griffiths...

Howard - Well, it's probably more likely that if you've got a tree adjacent to your house that it might be your house that's subsiding somewhat because, if you've got a tree growing on a clay soil, they can abstract water from it and that can sometimes in a dry summer make the clay shrink and cause subsidence. So maybe it's the other way round. But to answer your question which is where to plants get their minerals from? Why don't plants by taking out the minerals out of the soil cause the soil to reduce? You have to remember that plants are still 90-95% water and the mineral content is only perhaps about 1,000th of the plant dry weight. When you burn a log you get ash out which is very light, isn't it and that's the mineral content that's left after you've burnt that log. So, in actual fact, because of the relative uptake of carbon from the atmosphere which makes the plants grow, they don't absorb very much from the soil. At the same time, they're putting roots below ground which are building up the volume and so the earthworms are busy replenishing the minerals from the ground rock below.

Rubin Vase: Face-Vase Illusion

How do visual illusions work?

Neuroscientist Kate Storrs answered this deceptive question...

Kate - So yes, they're certainly happening in different parts of your brain. That's not necessarily the explanation for why some are switchable and some are not though. So, just to give a bit of background on why somethings have two interpretations. It's because they're fundamentally ambiguous similarly. There are cues to two different interpretations both within the image.

So this face/vase illusion that most people have probably seen. You can either see it as two black faces sitting on a white background or a white vase sitting on a black background. We know that in our visual system we have cells that respond to different bits of the visual field that respond to, for example, a white surface on a black background or a black surface on a white background. So, if I look at it and by chance the cells that like white things on black backgrounds are a little bit more active when I first glance at it, they have excitatory connections to other cells that have similar interpretations so they're going to win and form this coalition that's kind of self-reinforcing and then that will feed to higher layers and that will be interpreted as a vase.

Chris - Does it have the converse where when those ones get a bit more excited, as well as helping to excite other cells, they also turn off the cells that want to instead of a vase - they want to see a face?

Kat - Yes, absolutely - spot on. Because seeing as a white thing on a black background is incompatible with seeing it as black on white and so you have inhibitory connections between the cells that have those two different interpretations.

Chris - Dan.

Dan - The first time I saw that spinning dancer illusion. Where it's an animation of a dancer spinning and it appears to be spinning in one direction and then suddenly, for me anyway, she switched directions and I felt really nauseated when that happened. Is that common or.?

Kate - Yes. There's something very unnerving about your interpretation that had felt so solid and real suddenly completely switching.

Dan - Yes, your brain doesn't like that, I guess?

Kate - No.

Chris - The other one is that. Ah Gerry, go.

Gerry - It's an interesting cosmological consequence of this as well is that for pretty well all norther hemisphere cultures we talk about the Milky Way, so there's this white on dark sky. Yet, for the Aboriginal people of southeast Australia, they talk about dark on white. It's the dark bands through the middle of the Milky Way that form a gigantic Emu shape and they really do actually.

Chris - And don't they use that to know when it's in a certain position in the sky to know when to go and get the eggs?

Gerry - Absolutely, yes. It's cultural and it works very well but it's a nice inversion of black and white and which one you decide is the signal and which one you decide is the background is clearly just a cultural presumption.

Chris - Kate - one of the things which I've noticed when you look at that hollow mask illusion is that it's impossible to force yourself, even though you know, and by this I'm talking about if you see a mask spinning round, and you're seeing it from the front, and it turns round, and you see it from the back, at some point you know you're looking into the inside of the mask but you can't help yourself but to see it coming out at you. I know with this illusion where we've got this vase or the faces, I can cause myself to flick between the two but, with the hollow mask one, I just can't overcome that.

Kate - Yes. Your visual system takes a lot of prior knowledge into account and our experience with faces is that they're always convex objects, and they're such familiar patterns, we just see them compulsorily as being convex objects even if know, at some kind of intellectual level, that they're not.

Chris - So basically, it's your brain saying, I know what the world's all about and, therefore, I'm going to force you to see it one way regardless of whether that actually is the reality?

Kate - Yes. So to answer Cameron's question. I think the difficulty of voluntarily switching depends on how strongly these coalitions that represent the different interpretations are suppressing one another for some stimuli. The cues in the image seem to be such that there isn't very strong evidence for either interpretation and you can tilt them with eye movements or attention, whereas others like the spinning dancer, they're just totally compelling and antithetical interpretations.

Chris - Some people have found that individuals who have schizophrenia can't see these illusions - they don't experience them.

Kate - Yes, the hollow mask illusion in particular. There's evidence that schizophrenics see it veridically as being a hollow mask.

Chris - Why?

Kate - We don't know. Possibly something to do with a failure to incorporate prior knowledge as effectively into your interpretation of the world as healthy brains do.

Lightning bolt in the sky

Could lightning sour milk?

Gerry Gilmore got to grips with this old wives tale...

Gerry - It's really interesting this one. It's a classical old wives tale in the sense of old wives being established wisdom, and it goes back hundreds of years.

It became a major research endeavour in the late 1800s with hundreds of scientific papers written on the subject and it turned out it's true, or at least it was true! 

The reason is that lightning - it's a classic case of associating the dramatic variable with the answer when, in fact, there's some much more prosaic fundamental thing going on - the fundamental prosaic thing going on is first that in lightning storms you tend to have rain, and rain brings down germs and bugs and spreads them, out of the atmosphere.

Secondly, it happens in warm weather. So in the days before pasturisation and refrigeration, dairying was a marginal business and you took your life in your hands by eating milk and, in fact, it did go sour.

It was a well established phenomenon over millennia. All that changed about the year 1900 as pasturisation and refrigeration and it should no longer happen if reasonable sanitation applies.

From his vantage point high above the earth in the International Space Station, Astronaut Ed Lu captured this broad view of Hurricane Isabel.

Could the world be self healing?

We asked oceanographer Dan Jones to answer this question...

Dan - At the moment we do have some amount of the carbon dioxide that we put into the atmosphere does go into the ocean. It's roughly 20% of the amount that we emit is absorbed by the ocean and the other 30% roughly goes into the land and the other about less than half stays in the atmosphere. The term that you'll see thrown around is sinks of carbon dioxide. There's the oceanic sink and the land-based sink.

So the question is: can these sinks continue to do that job into the future? It's a big area of research right now and there's a ton of people working on it and a lot of effort going into this. so it's a really interesting question. I'd be careful about making too many summary statements just at the the moment but yes, it's a good question and there's a lot of work going into this.

Chris - We have evidence that this has happened in the past, haven't we? Because, for instance, we know that the Himalayas were formed when India, which was down near Antarctica, has migrated up across the Indian Ocean and it's pushed up the sea floor in front of it and made the Himalayas that way. Exposed lots of minerals from the sea floor and that's pulled carbon dioxide down out of the atmosphere and that triggered the ice age, didn't it?

Dan - Right. So these are very long term sinks of carbon dioxide. This is a geological one and these long term sinks take many thousands. ten thousand years, that kind of timescale to actually bring the carbon dioxide in the atmosphere down or back up, depending on which way that feedback mechanism is operating, so they're much, much slower.

The concern is that right now we're putting carbon dioxide into the atmosphere much faster than any of these natural sinks can get it back down very quickly. For example, that over the past million years we've seen 4-7 degree celsius temperature variations and these temperature variations are associated with these long sinks that you're referring to. But, usually, that temperature change of 4-7 degrees, those usually happen over about 5,000 year periods of time whereas right now in the past century, we've seen about a 0.7 degree celsius rise, which is ten times faster than the ice age recovery warming.

Chris - So you're saying that although we're seeing small changes in temperature, they're occurring over shorter timescales so, actually, the rate of change is much greater than we've seen in long timescales before?

Dan - That's the concern, yes.

Pedestrians walking in a city

What is the maximum human population?

Howard - The background of this is that we expect the global population is going to increase by 2-3 billion over the next 50-100 years or so, but we then predict it will level out to some extent. And as the questioner hints in their original question, we also expect we're going to see population's increasingly becoming urbanised, part of city dwellers and they're also going to want to have higher aspirations to lifestyle. So they going to want to increase their meat consumption and that is also not a very effective use of resources.

And then we've got planet change that we've been hearing about so we're going to get increased climatic extreme, floods and drought. So the question is, can we sustain the population that we are predicted to see?

Chris - Which is what?

Howard - We're currently heading towards 10 billion people. So we're about 6-7 billion at the moment and we're likely to head towards 10 by the end of this century.

Chris - People say we're consuming resources at the moment at the rate of two planet earths, not one. So, if you increase our numbers by another 30-50%, which is what that number you've just suggested is, that means we'll be up to three planet earths per person equivalent per year. That's totally unsustainable, surely?

Howard - It is dangerously unsustainable and that increases the threat upon our natural vegetation because there will be a demand to try to convert more land area into agricultural productive land, so it's a real threat all the way round. But then you can come back on us and say, well why don't we control the amount of food we waste? Up to 40 or 60% of the food that is bought in America and in Europe is just thrown away, it's not consumed. Why don't we learn to redistribute that food better?

Chris - Isn't that a short term solution though, Howard? Because if I feed more people, I'll get more people and we'll end up at the natural point where we've still got a population crisis albeit with a higher number of people ultimately anyway.

Howard - Well, coupled with this increasing population, we expect that there be increased education. There's going to be an increased awareness that you no longer need to have a huge family to support you in your dotage, as it were, and that actually small families are sustainable and they are realistic. So what we actually need to focus on is education and particularly empowerment of women. This is really important on a world scale to try to get cultural understanding that a huge family is not necessary.

Chris - You're a plant scientist though. I suspect you would love to see a solution to this problem lie with plants but there have been some people who've suggested that, in fact, if the entire world went vegetarian, this would immediately cut our carbon dioxide output by quite a significant amount. Because, if you look at the average westerner, we probably eat our own body weight in meat each year and, if you look at the rearing cycle for meat, we need about three years worth of supply. So, therefore, there's probably three times as much weight of animals as there is humans so you could immediately translate that into a very dramatic reduction if we all just stopped eating meat but, would we be healthy?

Howard - Yes, indeed. One small step we might care to take is to go vegetarian one or two days a week and this would start to change us to move towards a more sustainable diet, it would be better for our health as well.

Chris - The other possibility is in-vitro meat, isn't it? We've heard in the last couple of years we've had the in-vitro burger being made where people grow cells in a dish and make muscle artificially. Apparently, it doesn't taste too good though!

Howard - It looks pretty horrendous as well!

Chris - Okay, maybe I'll give that one a miss then!

Brain signals from the motor cortex of a monkey implanted with electrodes.

Is there any evidence for telepathy?

Kate Storrs answered this question for us...

Kate - Well, the literal answer to: is there any evidence for telepathy? Is yes. There's literature going back to late 1800s, some studies of which claim to have found some evidence for telepathy. The massive caveat on that is that if you consider this huge body of work as a whole, it's not compelling evidence for something as remarkable, as extraordinary, as telepathy.

Chris - What about the statistics of it that if you do enough studies then, just by chance, a few are going to throw up an apparent association and you're going to say, "ah look here's the evidence" and, of course, there's this bias in people publishing positive results? So they're going to say, "ah look I've got evidence for telepathy," they'll publish that whereas, if they didn't find anything they wouldn't publish. So, therefore if you look in the literature you're going to find more reports suggesting there's an effect than not?

Kate - Exactly, this is the main problem. The threshold we use, at least in psychology for whether an effect was found or not, is whether if you assume that the effect is not there you would have got a result as extreme or more extreme than this, less than one in 20 times. Is my data so surprising that I would only have found them one in 20 times if the effect wasn't there? But that means if there's not telepathy, if you run 20 telepathy testing studies, one of them will find an effect and, if you keep running them for hundreds of years, you will amass a very large number of studies that find positive evidence for telepathy. Combined with the second factor, the file drawer problem, we call it in science. If you find a boring result, if you fail to find something interesting like telepathy you have a tendency, with the best will in the world, to stick it in your lower file drawer and not quite get around to writing it up, or the journal are not quite so interested in publishing it. So, you end up with a very bias representation.

Chris - So have you looked at this literature? Is there any reason why it might be plausible or is there any evidence, or a mechanism put forward by people for how two brains that are not connected might be able to exchange information?

Kate - There's no mechanism within modern neuroscience that could account for it, no.

Chris - What about in physics, Gerry? Is there possibly a quantum entanglement possibility between two brains that could lead to a...?

Gerry - To be honest, this sounds a great deal more like astrology than physics.

Chris - So that's a no from both of you!

The top of a fizzy drink can

Could a can of cola stay cold for two days?

We asked Gerry Gilmore to help get Tacari out of trouble...

Gerry - Well the simple answer is that a can of cola, which you shouldn't be drinking for health reasons, will come to equilibrium in temperature with the environment very quickly indeed, because it's a very thin metal and it's just basically water and sugar on the inside, so it will quickly come to the ambient temperature. But that's irrelevant, the point is why does something feel cold? Something feels cold because it conducts heat away from your skin efficiently. So, on a cool-ish sort of day, if you touch a thin metal sheet it will feel cold to you.

Whether the second part of this was there was moisture on it (condensation), so therefore it was cold. Condensation has nothing to do with temperature, it's to do with humidity and so, if there was a cool-ish damp day, the cans could well feel damp and cold and that would just be their natural temperature.

Then there's the interesting follow-up of the car. Now, cars are interesting because cars over-cool at night time. That's because of their windows which radiate away more heat than is natural so cars get colder than their surroundings, which is why there's always ice on your car and not on the grass. But then they heat up more quickly than their surroundings as well. And so, if you went to check your can early in the morning in a car it would have been colder, and it would probably have frost on it, and he would have won the discussion, but doing it a little bit later means you lose.

So, the real answer is: a) by not having the cola for however long one was grounded and not having the other prohibitions, his health and general education has improved enormously. And secondly, there's three interesting bits of physics in that question which I hope have proved more interesting than the contents of can!

Floods in York

Can we store excess sea water underground?

We asked Dan Jones to if this theory had legs...

Dan - I like this question. I did a really simple, back of the envelope type calculation before the show so everyone please, feel free to go do you own and check this. So, we produce about 90 million barrels of oil per day and with the volume of that we could fill the O2 stadium 1,300 times per year, so fill it up and drain it about 1,300 times with the amount of oil that we produce. But looking at sea level rise, although the report of sea level rise is just a rate of 3.2mm per year, at the moment there's a lot of ocean out there. There's a huge surface area so if you look at just that 3.2mm over the entire volume of the earth, that is the entire volume surface area of the ocean, it's about 1,000 times more than the amount of oil that we produce. So it looks like no, there's not nearly enough room by about a factor of 1,000 unfortunately, and I don't even know if you could do this. If you could put the seawater in those places would it even stay there? The rock might be a bit more...

Chris - When we extract oil from the ground these rocks are porous rocks. They're like a sponge with oil in them and the way the oil is removed is by displacing it out, for the most part, with water already isn't it? So, one could argue that many of these oil wells are already saturated with water by the time you've recovered the oil so, it's a bit of a non-starter by the look of things. But thank you for those fantastic numbers.

High level Cirrus Clouds

37:38 - Blue Sky Sprites

Have you ever looked at the sky on a sunny day and seen tiny white dots wiggling in your vision?

Blue Sky Sprites
with Kate Storrs, The University of Cambridge

FameLab is a competition where scientists talk about an area of science that interests them for three minutes. Kate Storrs is the Cambridge FameLab champion for 2016 and she gave us her award winning talk... Cirrus Clouds

Kate - So, have you ever been looking up at the sky on a sunny day and noticed little specs drifting and wiggling and zipping around in your vision?

Chris - Many times.

Kate - Good. Well some of them are boring things. Some of them are just bits of gunk floating across your eye but others are something very special and strange and you can only see them against a bright blue light like the sky. So, next time it's sunny, look up and see if you can see tiny bright white dots. When you first spot them they look like sparks or pin pricks and then, as you watch for longer, you realise that each spark lives for about a second and then it wiggles along a little curvy path in that second and then pops out of existence.

Now, each one of those dots is an individual white blood cell moving through the veins in your eye. At the back of the eye you've got this tangled net of blood vessels that get infinitesimally narrow and the majority of things going down them are red blood cells, which are also tiny so they're fine. But, every once in a while a white blood cell comes along which is twice as big and it gets stuck for a moment in the narrow tubes and it has to squish and wiggle it's way free. So, if you happen to be looking at a bright light at that moment, you can see it getting stuck because the white blood cell is almost transparent. It lets the tiniest pin prick of light shine through and they're called blue sky sprites if you like whimsical names for things or Shearers blue field entoptic phenomenon, if you don't.

On top of the amazing fact that it means we can watch individual cells moving through our bodies, blue sky sprites have a couple of really surprising implications. So, first they show us that our eyes are back to front. That explanation I gave about white blood cells letting the light shine through only makes sense if the bit that detected the light was behind all the blood vessels but from a design perspective that seems crazy. It would mean that the light would have to pass through this whole tangle to get to the bit that mattered. But, crazy as it is, that's how the eye works or at least how it works in mammals and birds. If you were an octopus your eye would be the right way round and you wouldn't see blue sky sprites.

The other surprising implication is that we can watch our immune systems fighting disease. About ten years ago some scientists gave people a very small dose of e-coli bacteria. Just enough to trigger an immune response which means their bodies generated more white blood cells, and those people could see about 50% more blue sky sprites while they were fighting the e-coli than they could before.

For me though I love them because they're a reminder that science is not essentially high tech or complicated. At its heart science is about looking closely at things and even our most frivolous and personal experiences, gazing up at the sky on a sunny day can, if you really pay attention to them, turn out to contain whole worlds of surprising new knowledge.

Chris - Kate - why is this more apparent when you look at a nice bright blue sky than any other background?

Kate - Because your red blood cells are literally red, which means they absorb the blue light and so if you look at a blue light there's the largest spectral difference between what's being absorbed by the red blood cells and what's being let through by the white blood cells.

Chris - So it just makes the white ones much more apparent when you look at something that's a blue background?

Kate - Absolutely, yes!

Chris - Brilliant, thank you very much. And I can understand and now see why you did so well in FameLab. Thanks Kate.

Big Bang

Could the big bang be in a repeating cycle?

Astronomer Gerry Gilmore got to grips with this BIG question...

Gerry - That's a pretty big question just to sneak in like that Chris! The answer in principle is yes. We have a model, a description of cosmology and the origin of the universe in which the universe started as an infinitesimally tiny volume with a very, very large amount of energy in it indeed. This energy is actually from nothing, expanded very rapidly, much, much faster than the speed of light, for a longish time by its standards, about a millionth of a second by our standards. And that led to an universe that was incredibly stretched out and incredibly huge, and a teeny, teeny part of that original universe is what we see as our universe today.

Now that picture, when you plug it into Einstein's general relativity, provides an excellent description of all our observations, but it makes no sense at all. You have to make up all sorts of assumptions; you have to guess why numbers are the way they are. So that may be right but it's clearly not a complete description. We don't have a quantum gravity description of what really happened in those early days and so people are investigating all sorts of possibilities, even though there's no evidence, direct evidence as yet for it. One indeed, which in the jargon is called ekpyrotic, which is this idea that the universe is a repeating cyclic event and so we are on generation X of the universe.

So, as I say, there's no evidence for this but the current evidence is that the universe is accelerating its expansion and will accelerate into a universe of essentially nothing. So we've gone from intense concentration to intense cold permanent death, which is pretty dreary.

Chris - So it's blowing up and getting bigger but, the older it gets, the faster it grows?

Gerry - It's going faster rather than slower, yes. The weight of the universe ought to be slowing it down but something else is out there speeding it up. We don't know what this other stuff is. It's probably something similar to what happened in the very first instant of the universe - it's called inflation for obvious reasons. That inflation stopped, maybe this one will, maybe it'll turn round. Current lack of knowledge is that no that won't happen and bad luck, this is just all we've got. But it's quite possible, in the far future, the universe will be a much, much more interesting place than we think it will be today.

Why don't all trees drop their leaves?

We asked resident plant scientist Howard Griffiths to answer this one...

Howard - Okay. Well thank you very much. That's a great question because it's all, basically, a question of economics. To answer your first question: a tree 10 metres high might have 30 kilograms of leaves that it might shed. Bigger trees will have more, up to 100 kilograms of leaves, but leaves are costly to make.

So we heard earlier about the nutrients you need to take out from the soil to build together with the carbon to make the structural material. And they're also a risk in cold, snowy habitats because they interact with wind and they cause trees to blow over and they might cause water to be lost from the tree at a time when the ground is frozen. So, deciduous broadleaf trees, which we might recognise as Beech, and Oak, and Lime, they leaf out late in the year, at the end when the risk of frost has gone and, provided they've got plenty of water and nutrients, they can flush a new set of leaves every year and that allows them to grow faster than the evergreen conifers. So they outcompete the conifers when they grow side by side

So then, what about conifers? Well conifers tend to grow better in cold, waterlogged soils where nutrients are very infrequent, so they hold onto their leaves for two to three years and so the economics of building a leaf make more sense for a conifer to hold onto its leaves. Then they have a structure; they shed snow and so on in the cold winter and they're very tolerant of freezing and so on, but they're slower growing and so that's the trade off. Soo conifers are generally restricted high up mountains or up into the northern latitudes.

Western Lowland Gorilla

Could we breed gorillas to talk?

Kate Storrs pondered the possibilities of this question...

Kate - I love this question. If Donald would like to get in touch I think we should start writing the grant application!

Certainly people have taught great apes how to use sign language and how to use pictographic keyboards. They communicate can quite well in simple sentences but don't seem to have ever grasped grammar and syntax, or had that kind of vocabulary explosion that human children do. So there's clearly something missing in the non-human primate brain at the moment.

Donald said in his question: if you gave 50,000 years to do the selectively breeding programme, which is a very, very long time.

Chris - Longer than the grant you'd probably get funded for, that's true.

Kate - That's about 5,000 gorilla generations. If you go back 5,000 human generations, you go back about 100,000 years. We're mostly in Africa, we're still interbreeding with neanderthals, it's before the great kind of cultural explosion. A lot can happen in 50,000 years. With selective breeding, I'm going to go with yes!

rocket launch

Could we launch rockets from rockets?

Gerry Gilmore blasted off with this theory...

Gerry - Yes, is the answer. In fact, that's the way we do it. It's not the combined speed, it's the combined acceleration that matters but, eventually, you get to the combined speed. So, for example, when you're launching a big rocket you strap four or five small ones on. They're called boosters, and then you toss that up, and then you have a second stage, third stage, and so on. The cumulative speed is built up by adding rocket engines at various stages through the flight.

Once you run out of rockets there's another cute thing you can do which is bounce off a planet or the moon. You don't actually, physically, hit it but if you go really close then you can go down close to a planet and then zoom away.

Chris - This is what they call a "slingshot" isn't it?

Gerry - It's a "slingshot" yes. "Gravitational slingshot."

Chris - How does it work?

Gerry - Well, if you time your motion of the spacecraft appropriately, you can take a little bit of the energy out of the orbit of the planets. You slow the planet down slightly and speed yourself up so total energy is conserved but you transfer energy from the planet into the spacecraft.

Chris - But surely, if you're being attracted by something. If you're zooming towards a big planet, its gravity is accelerating you towards it, when you've gone round the other side of it and you want to get away again, isn't it just going to pull you back as hard as it pulled you in in the first place, so there's no net gain?

Gerry - It's all a question of relative motion and the fact that things are spinning as well helps to confuse things a lot as well. If you just imagined a stationary planet and you went down and came back up again then, yes, you'd gain nothing. You would, in fact, go in what is called an orbit around that planet round, and round, and round, as the moon goes round the earth, nothing would ever change. But, if you go very close to the planet and remembering the planet is moving compared to where you want to be so, in a different reference frame, then you can pick up some of the energy. So that's how you get to an outer planet like Jupiter or Saturn. You do it by heading into Venus and then you zoom around Venus at high speed and you get flicked out and that's the only way.

Chris - So you let Venus pull you in but, by the time you get to Venus, Venus has moved off somewhere else so you've just got the gravitational acceleration as Venus was temporarily there, and then you're on your way to somewhere else. And you do that a few times with a few planets and you can get a lot more speed than you would otherwise have with a rocket?

Gerry - That's absolutely correct, yes. It's just a question of precision timing and.

Chris - And it takes a long time, I presume, as well because you've got to keep zipping backwards and forwards on the solar system doing journeys of billions of kilometers instead of just going A to B?

Gerry - Yes, a typical mission to the outer planets will, actually, bounce off Venus and the Earth and Mars two or three times before it heads on out. So it's bouncing around the inner solar system picking up speed, and picking up speed until, eventually, it gets flicked out in the sling shot.

Chris - And it's still faster to do that, in terms of time spent, than just to have a really, really, really big rocket and accelerate yourself through a really, really, really high speed?

Gerry - No. In terms of time spent, if you were rich and you had a really big rocket, that's the way to do it but it's just a waste of money to do that when Isaac Newton can do it for you.

Chris - And, also, is there not more inherent risk because if you've got a really, really, really big rocket it's going to be a really, really, really big explosion if anything goes wrong and, also, you might as well take the lower risk pathway if you bounce off a planet like you're saying?

Gerry - Yes, it works. People have been doing it for a long time so we know how to do it, so it is cost effective. It does require some pretty cute calculations because you've got to know where everything is going to be at exactly the right time and the right place. But, that's what space scientists do for a living!

Baby Yawning

How many cell divisions make a baby?

Chris Smith got out a paper and pen to work through this one...

Chris - Well, actually, this comes down to pretty simple maths. Because, if we think about it, a single egg divides into two, and one cell becomes two, and then those cells each divide in half again. So two splits to make four and those four cells split themselves in half and they become eight. And then those eight cells split in half and you get 16 and then 32 and this grows exponentially; and that means we can write an equation to represent that growth where you say 2 to the power of n, which is the number of divisions, equals X cells. So, if we want to know what n is (how many divisions), we need to know how many cells. Well a baby contains, probably, a couple of trillion cells. So, therefore 2 to the power of n divisions must equal about 2 trillion.

So how do we find out what n is? Well you can do this using logarithms. So if we take the natural logarithm of both sides of the equation, you actually then get n x ln2 = ln(2 trillion). If we then divide both sides by the natural logarithm of 2 (ln 2) you get:

ln (2 x 1012) / ln2 and that's actually 28.34 divided by 0.693. That's about 41.

So, what that tells you is that a single cell only has to divide about 41 times to end up with 2 trillion cells that would make up a baby! It's not as many as you might think, is it?


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